In recent years, attention is being paid to a device called a metamaterial. The metamaterial is an artificial substance having an electromagnetic or optical characteristic which is not provided in substances existing in the natural world. Representative characteristics of such a metamaterial include negative magnetic permeability (μ<0), negative dielectric constant (∈<0), or negative refractive index (in a case where both of the magnetic permeability and the dielectric constant are negative). A region satisfying μ<0 and ∈>0 or a region satisfying μ>0 and ∈<0 is also called an “evanescent solution region”, and a region satisfying μ<0 and ∈<0 is also called a “left-handed system region”.
FIG. 10 is a four-quadrant diagram showing characteristics which appear with respect to waves incident on a medium by signs of the magnetic permeability μ and the dielectric constant ∈. Most of substances existing in the natural world correspond to right-handed media positioned in the first quadrant shown in FIG. 10. A wave incident on this medium is refracted only by a refractive index determined by the magnetic permeability and the dielectric constant and then propagates in the incident direction. In contrast, in the second and fourth quadrants (evanescent solution regions) shown in FIG. 10, the incident wave cannot propagate. In the third quadrant (left-handed region) shown in FIG. 10, the refractive index is negative, so that a wave incident on this medium propagates in a direction opposite to the incident direction.
As an example of realizing such a metamaterial, a split ring resonator (SRR) for microwaves is disclosed in “Left-handed metamaterial”, Nikkei Electronics January 2, Nikkei Business Publications, Inc., Jan. 2, 2006, p. 75-81”. In the split ring resonator, unit cells each made by two large and small ring patterns in which a part of the circumference is notched are periodically disposed. In the split ring resonator, resonance occurs in a specific frequency region, and μ<0 appears. By disposing the split ring resonator and a metal rod (∈<0) close to each other, μ<0 and ∈<0 appear, and a left-handed medium can be realized.
By making negative magnetic permeability appear, unnecessary electromagnetic waves emitted from an electronic device or the like can be suppressed. More specifically, when a magnetic flux enters a medium in which negative magnetic permeability appears, unnecessary electromagnetic waves emitted from an electronic device or the like can be reflected or suppressed.
Non-patent document 1: “Left-handed metamaterial”, Nikkei Electronics January 2, Nikkei Business Publications, Inc., Jan. 2, 2006, p. 75-81
However, in the split ring resonator as disclosed in the above prior art document, a conductor is formed in a plane, so that capacitance which is large enough cannot be obtained. There is a problem such that, to realize desired characteristics, the size becomes relatively large.